Gastric cancer (GC) is the leading cause of cancer death in Colombia, gastric tumorigenesis is a gradual and long evolution process involving genetic and epigenetic changes that activate protooncogenes and inactivate Tumor suppressor genes (GST). The genetic changes include loss of heterozygosity (LOH), microsatellite instability (MSI), translocations, aneuploidy, and mutations in GST; and mutations in protooncogenes or amplifications. Meanwhile, methylation of promoters is the commonest epigenetic alteration. Actually, CG is a public health problem in the country for three factors: high rates of incidence/mortality, overruns treatments for advanced disease stages and lack of public access to services health. This review the genetic and epigenetic alterations that are found more often in CG, and its association with different types of CG.